This invention relates to a method of recovering elemental phosphorus from phosphorus sludge and converting the residue into non-hazardous waste that can be disposed of safely. In particular, it relates to a process in which elemental phosphorus in sludge is separated from coarse solids by mechanical screening and melting, and is then separated from suspended solids using chromic acid. Coalesced phosphorus is recovered and the remaining solids are converted into non-hazardous compounds.
Elemental phosphorus is made commercially by heating nodulized phosphate rock mixed with sand and coke in an electric arc furnace. The phosphorus vapors are condensed in water and the liquid phosphorus is collected. A phosphorus sludge or mud consisting of elemental phosphorus, dirt, and water is an undesired byproduct of the process. The sludge is often deposited in ponds and covered with water to prevent the phosphorus from igniting. Since the sludge is considered to be hazardous, it must be rendered non-hazardous before it can be safely disposed of.